This disclosure relates to dishwashing machines of the type used in households and commercial settings having upper and lower racks within which are arranged articles to be washed. Ordinarily the lower rack is loaded with larger size plates, pots and pans, and the like, and the upper rack is particularly designed to carry the smaller dishes, cups and glassware. Such dishwashing machines normally have one or more spray arms which rotate on a horizontal plane having orifices or jet holes which spray the washing and rinsing liquid upwardly and or downwardly against the dishes in the racks thereabove or therebelow depending on the location of the arm itself. One or more of these orifices or jet holes may be positioned so that the water streams issuing therefrom cause the spray arm itself to rotate thereby achieving maximum coverage of the dishes by the washing liquid.
One of the problems associated with present spray arms, and associated water jets, is that they are typically either all on or all off. A reduction in water pressure and an increase in pump prime requirements usually results from attempting to increase total spray arm flow rate by adding additional jet holes to achieve additional spray arm coverage.
This disclosure attempts to solve a problem inherent to spray arms, including mid-spray or middle spray arms, in which, based on conventional technology, will only spray upward onto the underside of the upper rack, leaving only the lower spray arm as the primary means to wash the lower rack. For example, when using ‘single rack wash’ in upper rack mode, the upper rack receives downward spray from the upper spray arm, and upward spray from the mid spray arm. However, when applying the current process of ‘single rack wash’ to the lower rack, only the lower spray arm is utilized, thus only upward spray is produced from the underside of the lower rack.